Changing a domainname in ISPConfig 3 for an existing Webspace (SSH Hostname?)

On the ISConfig Webpanel I created a site with the domain "firstdomain.tld". Afterwards I changed the domain name to "seconddomain.tld". Everything seemed to work ok. I can reach the webspace with pointing my browser to "seconddomain.tld".

But still I got some issues:

When I connect by a new created Shell-User I get in the terminal "[email protected]" and not "[email protected]". I don't have any permissions on the shell. I guess it's caused by the use of the "firstdomain.tld" instead of the new "seconddomain.tld". Also on the Webspace, the User has not full permissions, I guess it depends on the same issue.

Is this a bug or isn't it possible to change the domain after creating a webspace?

How can I change the "virtual ssh hostname" from "firstdomain.tld" to "seconddomain.tld"? I couldn't find any entry in ispconfig DB or on the system. Where are the virtual SSH Users saved?